Process for the preparation of the cyanhydrin of formisobutyraldol



Patented Apr. 6, 1943 PROCESS FOR THE PREPARATION OF THE CYANHYDRIN F FORMISOBUTYRALDOL Kurt Warnat, Basel, Switzerland, asalgnor to Hoflmann-La Roche Inc., Nutley, N. 1., a corporation of New Jersey No Drawing. Application March 10, 1941, Serial No. 382,672. In Switzerland April 24, 1940 2 Claims.

a-Hydroxy-p,p-dimethyl- -butyrolactone, an important material in the synthesis 01! pantothenic acid, was first prepared by Glaser (Monatshefte flir Chemie, vol. 25, year 1904, page 47) by the action of hydrocyanic acid on formisobutyraldol and saponiflcation oi the resulting cyanhydrin. Later, Kohn and Neustadter (Monatshefte iiir Chemie, vol. 39, year 1918, page 296) improved this synthesis by reacting the bisulphite compound of aldol with potassium cyanide. Thus, Kohn and Neustiidter obtained from 80 grams and 93 grams oi aldol 50 grams and 65 grams of a-hydroxy-p,,B-dimethyl- 'y-butyrolactone, respectively, i. e., 49 and 55 per cent of the theoretical, respectively.

It has now been found that substantially higher yields 01' the lactone, amounting to about 90 per cent of the theoretical, can be obtained by changing the directions 01' Kohn and Neu- Example 51 grams mol) of iormisobutyraldol are dissolved in a solution of 1% mol of sodium-bisulphite while heating. The almost clear solution is then cooled to 10-15 C., a solution of 28-30 grams of sodium-cyanide in 70 cc. of water poured into it rapidly without further cooling and shaken immediately. A homogeneous solution is obtained which spontaneously reaches a temperature exceeding C. and from which an oily layer separates after a short time. The oil is removed and the aqueous solution which still has a temperature oi 25-30 C is three times extracted with 100 cc. oi. ether. The resulting cyanhydrin and the ether are added to cc. of concentrated hydrochloric acid while cooling and the product, after standing for a while, heated for 1 to 2 hours on a steam bath. After cooling, the acid solution is treated with 50 grams of potassium carbonate and a little ice. The product is then shaken 8 times with 100 cc. of amylene hydrate each time, the amylene hydrate dried and evaporated in vacuo. The residue is distilled in vacuo. 57 grams or a-hydroxy-fifl-dimethylbutyrolactone are obtained, 1. e., per cent of the theoretical. The lactone boils at 122-125 C. at a pressure of 12-14 mm.

I claim:

1. In a process for the preparation of the cyanhydrin oi iormlsobutyraldol, the steps which comprise bringing a solution of iormisobutyraldol-bisulphite to a temperature of approximately 10-15 C., adding thereto a water soluble cyanide under such conditions as to cause the temperature to rise immediately and spontaneously to between about 30-70 C., and permitting the reaction to proceed to completion within such temperature range.

2. The process recited in claim 1 in which the added agent is sodium cyanide.

KURT WARNAT. 

